The pictures above showed, what can be calculated or measured on the surface of the airfoil. To get a better feeling, how the velocity in the vicinity of the airfoil looks like, the following image illustrates the flow field around the airfoil. The pressure changes, introduced by the airfoil, can be felt all around the airfoil, for subsonic flow even in front of the airfoil.
 Calculated flow field around the MH 60 airfoil with -5.0º flap deflection at 6º angle of attack. The red stream traces show the local flow direction. The background colors show the pressure field with high pressures in red and low pressures (suction) in blue. The solution was calculated by solving the Euler equations with DLR's »Flower« code. |
Due to the large, negative flap deflection, the `lifting´ force of the airfoil is directed downwards. The positive pressure near the leading edge (red, Cp = +1.0) indicates the location of the stagnation point, whose position can be assumed between the dividing streamlines. Another area of high pressure is visible on the upper surface in the concave corner, caused by the flap deflection. The convex corner on the opposite side of the flap causes high velocites and thus low pressure (blue). Both regions together are the main cause for a clockwise torsion moment, which results in a positive moment coefficient cm.
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